Last week, the AFL-CIO and the Chamber of Commerce worked out a guest-worker compromise that lets in foreign workers on a sliding scale of 20,000 to 200,000, depending on the strength of the economy.

Nice deal. As are the other elements of the Senate's bipartisan Gang of Eight plan — the expansion of H-1B visas for skilled immigrants, serious tracking of visa overstayers and, most important, a universal E-Verify system that would make it risky for any employer to hire an illegal immigrant.

But there's a rub.

It's the perennial rub. Are Democrats serious about border enforcement? It's supposed to be the trigger that would allow illegal immigrants to start on the path to citizenship.

Why is a trigger necessary? To prevent a repeat of the 1986 fiasco where amnesty was granted and border enforcement never came — giving us today's 11 million living in the shadows.

Yet just a week ago, Homeland Security Secretary Janet Napolitano, referring to border enforcement, averred that "relying on one thing as a so-called trigger is not the way to go."

Regarding legalization, "there needs to be certainty." But not for border security?

And she's the person in charge of securing that border.

Now listen to President Obama: "Given the size of the border, it's never going to be 110% perfect. What we can do is to continue to improve it."

The usual Obama straw man. Who's asking for 110% enforcement?

And the need is for something a lot more than just improvement.

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The objective is to reduce a river to a trickle. It's doable. The two sections with triple fencing outside San Diego have reduced infiltration by 92%.

To be sure, the Gang of Eight enforcement trigger is not ideal. The 11 million get near-instant legalization — on the day, perhaps six to nine months after the bill is signed, when Homeland Security submits a plan (with the required funding) to achieve within a decade 90% apprehension and 100% real-time surveillance.

This plan triggers "probationary" legalization, which in reality is permanent, because once the 11 million register, it is inconceivable their status would be revoked.

Let's be clear. A mere DHS enforcement plan is a very weak trigger. I would prefer legalization to occur later, once the plan is actually carried out and some independent body certifies that the border is essentially closed.

But that simply will not happen. Democrats control the Senate and the White House, and they will only agree to a weaker trigger. Which is? Legalization first — i.e., living here openly without fear of deportation but nothing more until the border is controlled.

Until then, no one even starts on the path to citizenship — no green card, no naturalization.

So why is Obama undermining even that compromise, asserting that "this earned pathway to citizenship" must not be "put off further and further," that it must be "certain" — not contingent on verifiable benchmarks of border closure?

Are he and Napolitano signaling to their hard-core open-border constituency that they will try to sabotage passage of any law that has a serious enforcement trigger, or that they will try to sabotage enforcement if a strict law is nonetheless enacted?

Why? Isn't border control an elementary principle of sovereignty?

What country deliberately forfeits the right to decide who gets to join its communal life?

Remember: We're not talking about the 11 million already here who will be legalized as a matter of both practicality and compassion. We're talking about the next 11 million. Without border enforcement, they will be here.

If you don't build it — the fence, the visa-tracker, E-Verify — they will come.

Why deliberately create the next immigration crisis? Is it because you coldly calculate that this wave and the next are destined to be partisans of your political party? Talk about placing party over country.